ST Sig fuse missing from the fusebox.. what does it do?

ST Sig fuse missing from the fusebox.. what does it do? - Mazda MX-5 (Mk1 / Mk2) Forum

Checked out the fusebox in my MX-5 NB today. The 10A fuse for the ST Signal is missing. From what I can understand it controls the fuel pump signal or something like that when I start the car.

It came without it when I bought it I suppose, and it runs fine right now, nothing unusual. What does it do? Can I put in a fuse or has the previous owner done some rewiring and do I run the risk of frying something important?